transmission module

The amplitude-modulated band (AM band) contains the radio waves having frequency of less than 30 MHz or having wavelength of 10 m or more. The lower atmosphere is more or less transparent to radio waves. However, the ionosphere reflects back the radio waves. Thus, a signal emitted by an ..

In earlier times, the most widely used form of communication was a system based on the transmission of a continuous-wave (CW) signal. With this system, the signal was interrupted periodically (Morse code) to produce a coded message. The CW systems required tremendous training and expertis..

In this type of modulation, E c , w c are kept constant. The phase angle q of the carrier wave is varied according to the modulating wave. The common name for "phase modulation" and "frequency modulation" is "angle modulation". The digital ..

Need for Frequency Modulation - (i) Various electrical machines and noises cause amplitude disturbance in the transmission of amplitude-modulated wave. This makes the reception noisy. So, there is a need for different type of modulation, which can reduce the ..

It translates the sampled amplitude data into a code. The code is transmitted as a succession of pulses and spaces. The system enjoys greater freedom from noise and interfering signals than is possible with most other pulse systems. This freedom arises from the fact that it is merely necessary to ..

The simplest approach to the design of modems is to treat the entire PSTN as a linear analog network. [Note that PSTN is almost entirely due to the use of pulse-code modulation (PCM) for the transmission of voice signal..

One desirable feature of radio transmission is that it should be carried without wires (i.e.,) radiated into space. At audio frequencies, radiation is not practicable because the efficiency of radiation is poor. However, efficient radiation of electrical energy is possible at high freque..

Elements of a Communication System..

For high fidelity reception, the audio frequencies from 20Hz to 20000Hz must be reproduced. This requires a bandwidth + 20000Hz i.e., 40000Hz. (Note that both the sidebands must be reproduced). The bandwidth actually assigned for AM transmission is 20000Hz. This is done to keep the inter..

Symmetric Modem Configuration - The simplest approach to the design of modems is to treat the entire PSTN as a linear analog network. [Note that PSTN is almost entirely due to the use of pulse-code modulation (PCM) for the transmission of voice signals..